Chestpiece:The Dual-Head chestpiece and full-rotational Acoustic Valve Stem are machined and polished to the exact tolerance from the finest stainless steel. The Diaphragm is fitted with an ultra-sensitive Diaphragm sealed by the Diaphragm Retaining Ring to produce optimum amplification and high frequency transmission of heart and lung sounds at 100 to 1000Hz. The extra large and deep cone-shaped Bell detects acoustic sensitivity at low frequency sound transmission at 20-100 Hz. Diaphragm and Bell are crowned with a non-chill durable PVC Diaphragm Retaining Ring and Bell Ring to provide greater patient comfort.